Fox Sports will be able to carry as many as 18 regular-season games showing the popular New York Yankees on its national TV channels starting in 2014, which is significantly more than the 12 that ESPN will be allowed to produce.

But Fox will be limited to only eight Boston Red Sox games.

That’s because of a provision in the MLB media rights deal it signed last year, which allows Fox to show 26 local RSN-produced games on every Saturday during the regular season via its national cable channel, which is certain to be Fox Sports 1.

The little-known clause allows Fox Sports 1 to carry 26 games between two teams that have each sold their local rights to Fox Sports-owned RSNs. That means Fox Sports 1 could show the Tigers (FS Detroit) against the Angels (FS West) or the Yankees (YES Network) against the Indians (SportsTime Ohio).

But teams like the Red Sox (NESN), Phillies (Comcast SportsNet Philadelphia) and Orioles (MASN) will not have any of their local games carried on Fox Sports 1 because Fox does not control local rights to those teams.

Under the terms of the eight-year deal that pays MLB an annual average of $525 million, Fox will have 52 regular-season baseball windows on Saturdays each season: 12 on its broadcast Fox channel and 40 on a national cable channel, which will be Fox Sports 1, the rebranded Speed.

Of the 52 games, Fox Sports 1 is allowed to televise nationally 26 games a year that involve two teams scheduled to be carried regionally by FSN. Fox and MLB have not determined how many of those games can involve a single team yet. But sources say Fox should be able to carry at least 10 games of any one team, such as the popular Yankees.

On top of those 26 windows, Fox and Fox Sports 1 have 26 other windows that are split between broadcast and national cable channels, which limits single team exposures to eight. Combine those eight games with the 10 local FSN games, and Fox winds up with a national package that should help broaden the appeal of its new channel, particularly with cable systems that don’t want to carry it. Speed is in 81 million homes, well behind ESPN and ESPN2, which are in 99 million homes each.

In one of the more interesting and potentially controversial developments, a source said Fox Sports 1 plans to black out games on the local RSN when they are carried on Fox Sports 1. That means that Yankee fans in New York will have to turn to Fox Sports 1, not YES, to see the games that are moved. Fox Sports 1 plans to carry the local feed, most likely from the home team’s market.

Fox has not determined how it will share advertising revenue with the RSNs that will be blacked out.

It’s also not known how distributors will react to having games on their most expensive channels blacked out. According to figures from SNL Kagan, FS North, which carries the Twins, has a license fee of $4.26 a subscriber per month. Fox Sports West, which carries the Angels, is $2.68. Cable and satellite operators paying such a high fee for regional sports networks are certain to be angry about losing high-rated games, even if they are moved to another channel on their service.

Fox holds the local rights to some of the most popular teams in MLB. Last season, MLB’s three biggest local ratings involved Fox Sports Network teams: the Tigers (FS Detroit), Reds (FS Ohio) and Cardinals (FS Midwest). The Yankees (YES Network) regularly have the biggest average audience of any MLB team.

Fox would not comment for this story. It still has not officially announced plans to morph Speed into Fox Sports 1 this summer.

Sources said to expect a formal announcement to come soon after Fox completes its carriage deal with the country’s biggest cable operator, Comcast. At deadline, the two still were negotiating a long-term carriage deal that is expected to close this month.